MR spectroscopy (MRS) is used for the non-invasive study of cardiac metabolism without the need for the application of external radioactive tracers, such as involved in Positron Emission Tomography (PET). Nuclei of interest for metabolic MRS studies include 1H, 13C, 19F, 23Na, 31P, 39K, 87Rb. Both 31P and 1H-MRS-studies are of clinical interest. Specifically, 1H-MRS is used to measure total creatine and to evaluate the oxygenation of cardiac tissue or to evaluate diet and therapy effects. Also 31P-MRS is used to estimate the energetic state of the heart by analyzing cardiac high-energy phosphate metabolism. In principle, many clinical questions can be addressed with cardiac MRS. However, 31P is the most widely investigated nucleus in cardiac MRS study and is used for determining the T1 relaxation times for Phosphocreatine (PCr) and γ-ATP (adenosine triphosphate), which are used for correcting for the effects of radiofrequency saturation on metabolite ratios such as a PCr/ATP ratio.
Performing clinical cardiac spectroscopy involves a number of problems. Total examination time is relatively long, and motion artifacts including signal contamination by surrounding tissue (chest wall, blood pool) require correction. Motion artifacts from cardiac and respiratory motion have a negative effect on the reliability of myocardial 1H MR spectroscopy. Motion of the heart relative to the volume of interest may lead to reduced spectral resolution and contamination of the 1H MR spectrum by, for example, epicardial fat. In addition, respiratory motion may negatively influence 1H MR spectral resolution by preventing optimal shimming and water suppression. A system according to invention principles addresses these deficiencies and related problems.